This invention relates to a double central chain belt assembly for a chain scraper conveyor, said assembly comprising scraper members arranged at spacings from each other and each comprising a central portion and two outside portions of the same configuration as each other, and chain portions connecting the scraper members together, each adjacent pair of scraper members being connected together by a pair of chain portions which are arranged at respective sides of the centre of the assembly, each end of each chain portion terminating in an end link which serves as a connecting link.
German patent specification No. 1 291 709 discloses a double central chain belt assembly for a chain scraper conveyor of the type set out above. In that arrangement the central portion is in the form of a chain lock member which has legs at both sides. The chain lock member has two openings which are disposed at a small spacing from each other and those openings, as considered in the longitudinal direction of the chain, are of a length corresponding to the internal length of a chain link lying in a flat condition. A scraper flight is fitted on to the leg of the chain lock member at each side and fixed in position thereon by means of a screw. That chain belt is driven by means of a suitable chain drum having teeth which engage the chain links which are lying flat, with the result that the chain links which are in an on-edge position are subjected to a correspondingly high wear-inducing loading by the teeth of the drive drum.
German patent specification No. 2 755 880 describes a double central chain belt assembly for a chain scraper conveyor which involves a curved region in the trough of the conveyor. In that arrangement the double central chain belt comprises belt elements which are connected together by means of joints which permit suitable compensating movements, with two chain lines defined by the belt elements being in juxtaposed relationship. Arranged at the one end of the respective belt elements are scraper members which are supported against the side wall of the conveyor trough in the curved region thereof. Furthermore, provided at the other ends of the belt elements are connecting bridge members. The one ends of the belt elements are secured to the side, which faces towards same, of the scrapers members, by way of pivotal connecting means. Force is applied to the double central chain belt to produce the driving movement thereof, only at the connecting bridge members. It will be seen therefore that as that double central chain belt is capable of negotiating a curve, it is generally too expensive for a chain scraper conveyor without curves.
Another form of double central chain belt assembly for a scraper conveyor, as disclosed in German patent specification No. 838 124, involves a double chain belt having two chain lines comprising a plate-type chain. The chain comprises a plurality of elements of given length, which are connected together by way of movement-compensating joints. In that arrangement, at one side each element has a limb with an eye portion while at the other side it has a fork portion, the eye portion and the fork portion being pivotally connected together by way of a connecting pin. At the one ends of the elements, entrainment arms are secured by screws to the respective outermost plate chain links at both sides of the chain. The chain belt is also capable of negotiating a curve and therefore has features which are unnecessary for a chain scraper conveyor without curves.
In still another form of double chain belt assembly for a scraper conveyor, as disclosed in German laid-open application (DE-OS) No. 2 013 089, scraper members are secured at given spacings to two oppositely disposed chain links of the two chain lines. A compensating joint is disposed between the two chain lines between each two adjacent scraper members. That permits automatic compensation in respect of length and force in the two chain lines. That chain belt is required to be driven by chain drums which engage directly into the chain and cause a high rate of wear in respect of the chain and the chain drums.